1. Field of the Invention
This invention relates generally to the field of computer-aided design (CAD) systems, and particularly to a system for rendering three dimensional objects with surface textures applied thereto.
2. Prior Art
The runaway increase in computer performance/price ratio in recent years has made sophisticated CAD systems available to nearly anyone. Such systems have evolved beyond those intended for use by professional designers and engineers to include a wide variety of consumer applications. For example, CAD systems have been developed for providing point-of-sale demonstrations of product features and options. One application for such a system allows prospective purchasers of furniture to view an item in any of the available finishes or fabrics prior to making a purchase decision.
Texture mapping is a well-known feature of computer graphics systems. In a typical system, a three-dimensional object to be rendered is modeled with a wire frame defining a large number of polygonal surface areas. A mapping function is then determined between a two-dimensional (u,v) texture space and the three-dimensional (x,y,z) object space. Conventional texture mapping processes utilize various projection methods, such as cubic, cylindrical or spherical. One of the primary objectives of these methods is to cover the object surface or parts thereof with seamless texture. Each of these conventional methods introduces some degree of texture distortion as a necessary cost of seamless texture mapping. This is acceptable in most applications where relatively uniform surface textures are desired.
In many other applications, the distortions inherent in prior art projection methods are not acceptable due to the appearance of elasticity in the surface. If the texture mapping is intended to depict a relatively inelastic surface covering on an object, such as fabric on upholstered furniture, seamless mapping is not required. Indeed, seams are a desirable artifact contributing to a more realistic appearance.